A hotel-style master bathroom suite in an Edwardian semi in Hampstead, London NW3 — full reconfiguration with a freestanding stone resin bath beneath the window, a walk-in wet zone in marble-effect porcelain, twin marble-topped vanity with backlit anti-fog mirrors, brushed brass fittings throughout, and dimmable feature lighting on three switched circuits. Five-week fixed-price programme, full tank flood-test pass before any tile was cut.
A professional couple in their early fifties on one of Hampstead's quieter side streets, occupying a substantial four-bedroom Edwardian semi they have owned for eighteen years. Two grown-up children moved out within the last two years and the house had been progressively reset around two adults rather than four. The previous master bathroom — a 2008 refit with a P-shaped over-bath shower, mismatched tiles, and a narrow single vanity — had served the family well for fifteen years and was the last room in the house still wearing its early-2000s aesthetic.
The brief was hotel-style, but specifically a particular hotel they had stayed at the previous summer where the bath sat freestanding in front of a window, the wet zone was uninterrupted by shower trays or step-ups, and the brass fittings had a soft brushed finish rather than a polished mirror chrome. The room is 14m² and the existing layout used roughly a third of that on poorly placed fittings. Full reconfiguration was the right answer — new soil routing, new water supply runs, new layout, new everything below floor level as well as above.
We were one of two contractors quoting. The competing tender was £6,400 cheaper. We won the work because our methodology was the only one to (a) include full Schluter Kerdi tanking with a 24-hour flood test before any tile was cut, signed off as a separate work package, and (b) cost the joist doubling required for the freestanding stone resin bath into the fixed price rather than flagging it as a likely variation. Five weeks on site. Family bathroom remained in service throughout. The clients had their first bath in the new suite on the Friday evening of week five.
The brief was developed over two design meetings, with mood-board references and a specific hotel suite the clients had stayed in. Priorities, in their stated order:
A 5-week master bathroom of this scale and spec is achievable, but unforgiving. Six interrelated constraints had to be locked down before strip-out began.
The walk-in wet zone has no shower tray — the porcelain tile is the floor, falling to a linear drain at 1:80 over the wet-zone footprint. We installed a Schluter Kerdi waterproof membrane system across the full bathroom floor and 1.8m up the wet-zone walls, sealed at every penetration, then flood-tested for 24 hours with a 30mm standing water depth before a single tile was cut. Photographs at start and end of the test, signed-off sheet in the project file.
Full reconfiguration moved the WC position 2.1m from where it had been. The new 110mm soil run had to maintain a minimum 1:40 fall to the existing soil stack and pass through the existing floor void without compromising the joists. We routed the soil pipe parallel to the joist run, notched within building-control limits, doubled one joist where the run crossed perpendicular, and pressure-tested the new soil run before reinstating the floor.
A freestanding stone resin bath weighs roughly 110kg empty and around 380kg when filled and occupied. Standard Edwardian joists, even C16 timber at 400mm centres, have margin but not abundance for that point load. We surveyed the existing joist span and depth, identified a section where load-spreading was prudent, and doubled the joist over a 1.6m run beneath the bath position. Cost included in the fixed price, not flagged as a variation.
1200 × 600mm porcelain slabs are an installation craft in their own right. They need 18mm WBP plywood backing reinforcement between studs and tile-bed, full-spread adhesive (not dab-and-dot), continuous pattern matching at internal corners, and mitred external corners cut to 45 degrees on a wet-saw with a polished arris. We used a specialist large-format tiler for four days on site and pattern-walked every wall before adhesive went on the back of any slab.
Bathroom electrics follow strict IP zoning under BS 7671: Zone 0 (inside the bath) requires SELV 12V, Zone 1 (above bath, inside shower) requires IPX4 minimum, Zone 2 (within 600mm horizontally) requires IPX4. The backlit mirrors, shaver socket, towel rail and feature lighting were each zoned and specified to minimum IP44, IPX4 or higher as required, and the supplementary equipotential bonding to all metalwork was tested and documented at second fix.
The bathroom shares a stud wall with the master bedroom. The clients didn't want to hear the WC flushing or the bath filling from the bedroom side. We rebuilt the existing stud wall: 92mm metal stud, two layers 12.5mm acoustic plasterboard each side, 100mm acoustic mineral wool core, AcoustiSeal at perimeter and around all penetrations. Calculated Rw figure 50dB — better than most party walls.
Master bathrooms succeed or fail on the parts you don't see. The stone above the floor is the photograph; the tanking, falls, soil routing and joist load-paths underneath are the project. Our approach was structured around that distinction from first survey to handover.
Tanking as a separate, signed-off workstream. Most domestic bathroom builds tank casually — a coat of liquid membrane, a quick check, on with the tile. Our specification was a Schluter Kerdi sheet system with mechanical-fixed kerb at the wet zone, full corner detail, sealed at every penetration, and a 24-hour static flood test with photographic record at start and end. Signed-off sheet in the project file before any tile was cut. If the tank fails after handover, it isn't going to be ours.
Sub-floor work modelled and signed before strip-out. Soil routing, water supply runs, joist doubling for the freestanding bath, UFH layout, and acoustic stud framing were all modelled and drawn before the existing bathroom was opened up. The clients saw a single combined drawing showing where everything would run in the void below the floor, not a verbal explanation of "we'll work it out when we get under there." Two of the six callout-card constraints above were resolved in design, not on site.
Specialist tilers for the large-format slab work. 1200 × 600 porcelain isn't standard tiling; it's its own trade. We brought in a specialist large-format tiler for four days, pattern-walked every wall before adhesive went on the back of a slab, and the lead tiler personally cut every external mitre. The wet-saw needs a 1500mm bed and a polished-arris-finishing diamond. None of that is in a generalist tiler's kit.
Family bathroom protected throughout. The family bathroom next door stayed in active use the full five weeks. Dust separation at the master bathroom door, no dust-generating trades while the family bathroom was occupied (early morning and evening), and a daily 4.30pm tidy and dust-down before the clients came back upstairs. The family bathroom didn't lose a single shower window through the build.
Twenty-five working days from strip-out to handover. Every workstream sequenced against a Friday-evening occupancy target on day 25, with the 24-hour tank flood test pre-built into week 3 as a hard hold-point.
Existing master bathroom stripped to studs and joists. Detailed joist survey: spans, depths, condition, run direction. Stud wall to bedroom rebuilt as acoustic-rated 92mm metal stud with 100mm mineral wool core and double 12.5mm acoustic plasterboard each side. AcoustiSeal at perimeter. Joist doubling installed beneath proposed freestanding bath position, 1.6m run.
110mm soil pipe rerouted parallel to the joist run with 1:40 fall to the existing stack, pressure-tested. Hot and cold copper supply runs to bath, twin basin, WC, and walk-in zone — all in continuous lengths with no underfloor joints. Wet UFH manifold positioned in the airing cupboard, pipework laid at 200mm centres across the bathroom floor. Electrical first fix: bathroom-zoned circuits, supplementary bonding to all metalwork.
UFH-compatible self-levelling screed poured Monday over the cured first-fix layer. Schluter Kerdi tanking applied across full bathroom floor and 1.8m up the wet-zone walls, sealed at every penetration with proprietary corner pieces and pipe collars. Linear drain set at the back of the wet zone with the falls profiled in to give 1:80 fall across the showering area. Wednesday: 30mm standing water flood test introduced. 24 hours later: water level unchanged, photographs taken, tank passed and signed off.
1200 × 600 marble-effect porcelain slabs installed by specialist tiler over four days. Pattern-walked every wall before adhesive. Full-spread adhesive on every slab, not dab-and-dot. External corners cut at 45-degree mitres on a wet-saw with polished arris. Floor laid last, in continuous pattern matched to the wall vein. Grouted Friday with a colour-matched flexible grout, sealed Saturday morning.
Freestanding stone resin bath positioned on the doubled-joist zone, brass bath filler installed, supplies and waste connected. Twin vanity built up on hardwood plinth, marble worktop fitted, basins set and brassware connected. Wall-hung WC and concealed cistern completed inside the tiled duct with sensor flush. Walk-in zone overhead and hand-held shower set installed. Brushed brass towel rail and accessories. Backlit anti-fog mirrors mounted, IP-zoned electrical fittings commissioned, three lighting circuits balanced and dimmable. Snag walkthrough Friday afternoon. Handover Friday at 5pm. First bath taken that evening.
The technical detail behind a master bathroom suite designed around materials that age well and waterproofing that doesn't fail.
1700 × 800mm stone resin freestanding bath, double-skinned thermally insulated, matt white finish. Positioned on centre line of the rear window. Brushed brass floor-mounted bath filler with diverter and hand-held shower handset.
Open walk-in zone with no door. Single fixed 10mm tempered glass panel, 2000mm tall, brass profile fixings to wall and floor. Linear drain at rear, fall 1:80 across wet zone footprint. Brushed brass overhead rainfall head plus separate hand-held shower on rail.
1200 × 600mm marble-effect rectified porcelain, large-format. Continuous pattern-matched across walls and floor. Mitred external corners with polished arris. Colour-matched flexible grout, sealed at completion. Sealed perimeter movement joints behind silicone bead.
Twin marble-topped vanity, real Carrara honed marble, 30mm thick, soft pencil-edge profile. Twin under-mount basins. Vanity carcass painted soft warm white, built up on a 60mm hardwood plinth with brass toe-kick detail. Brushed brass push-open drawer fronts.
Schluter Kerdi 200 sheet membrane across full bathroom floor and 1.8m up wet-zone walls. Proprietary corner pieces and pipe collars. Mechanically fixed kerb at wet zone perimeter. 24-hour static flood test passed and signed off before any tile installation. Project file copy retained.
Wet UFH system, 12mm pipe at 200mm centres, 50mm screed cover under the porcelain. Single-zone control via Heatmiser Neo Smart thermostat. Surface temperature limit 27°C. Heated towel rail dual fuel: wet system (winter) plus electric element (summer use).
Three switched and dimmable circuits. Ambient: ceiling-recessed IPX4 LED downlights at 3000K. Task: backlit edge-lit anti-fog mirrors above each basin, integrated demister pads, all rated IP44. Accent: under-vanity-plinth LED strip plus over-bath surface-mounted brass fitting (Zone 1 IPX4).
92mm metal stud, two layers 12.5mm acoustic plasterboard each side, 100mm Rockwool RW3 mineral wool core, AcoustiSeal at perimeter and around all penetrations. Calculated Rw 50dB. WC flush and bath fill substantially inaudible from the master bedroom side.
A 14m² hotel-style master bathroom suite delivered against a 5-week fixed-price contract, with no variation orders, a 24-hour tank flood test passed and signed off before any tile was cut, the freestanding stone resin bath sitting on a doubled-joist zone the clients never had to know about until reading this page, and the family bathroom next door still in active use throughout. The walk-in wet zone runs continuously into the bathroom floor with no step-up and no shower tray. The marble-effect porcelain reads as one continuous surface from wall to floor.
The brass fittings have already started to develop the soft brushed warmth the clients wanted — six months from handover and the bath filler will look noticeably warmer than it did on day one, which is the trajectory the spec was chosen to deliver. The acoustic stud upgrade between bathroom and bedroom means that, for the first time in eighteen years, one of the clients can have a bath at 6.30am without waking the other. That outcome was not on the original brief but turned out to be the change they have mentioned most often since handover.
We had two contractors quote. The other one was six thousand pounds cheaper and we were genuinely tempted. Two things tipped us towards Building Group. First, their methodology document explicitly costed in the joist doubling for the freestanding bath; the cheaper quote had it as a possible variation that they'd "look at when they got under the floor". Second, they wrote in the 24-hour tank flood test as a signed-off work package before any tile was cut, with photographs at start and end. Both of those felt like they took bathroom waterproofing more seriously than anyone else we'd spoken to. Five weeks later, we have the room we asked for. The brass fittings are already softening to the colour we hoped they would. The bath sits exactly on the centre of the window. And the genuinely unexpected outcome is that the new acoustic stud means I can have a bath at 6.30am without waking my husband, which after eighteen years in this house feels like a small miracle. We'd recommend them without hesitation.
If you're thinking about a hotel-style bathroom suite, a freestanding bath, a walk-in wet zone, or a full reconfiguration of an existing bathroom, we'll come out for a free design consultation, walk the property with you, and put a fixed-price design-and-build proposal — including the joist work, soil routing and tank flood-test methodology — on your kitchen table within ten working days.
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